Polyporales

The Polyporales are an order of about 1800 species of fungi in the division Basidiomycota. The order includes some (but not all) polypores as well as many corticioid fungi and a few agarics (mainly in the genus Lentinus). Many species within the order are saprotrophic, most of them wood-rotters. Some genera, such as Ganoderma and Fomes, contain species that attack living tissues and then continue to degrade the wood of their dead hosts. Those of economic importance include several important pathogens of forest and amenity trees and a few species that cause damage by rotting structural timber. Some of the Polyporales are commercially cultivated and marketed for use as food items or in traditional Chinese medicine. The order was originally proposed in 1926 by German mycologist Ernst Albert Gäumann to accommodate species within the phylum Basidiomycota producing basidiocarps (fruit bodies) showing a gymnocarpous mode of development (forming the spore-bearing surface externally). As such, the order included the ten families Brachybasidiaceae, Corticiaceae, Clavariaceae, Cyphellaceae, Dictyolaceae, Fistulinaceae, Polyporaceae, Radulaceae, Tulasnellaceae, and Vuilleminiaceae, representing a mix of poroid, corticioid, cyphelloid, and clavarioid fungi. In a series of publications in 1932, E.J.H. Corner explained the occurrence of different types of hyphae in the fruit bodies of polypore fungi. He introduced the concept of hyphal analysis, which later become a fundamental character in polypore taxonomy. The order Polyporales was not widely adopted by Gäumann's contemporaries; most mycologists and reference works preferring to use the catch-all, artificial order Aphyllophorales for polypores and other 'non-gilled fungi'. When an attempt was made to introduce a more natural, morphology-based classification of the fungi in the 1980s and 1990s, the order was still overlooked. A standard 1995 reference work placed most polypores and corticioid fungi in the Ganodermatales, Poriales, and Stereales. Molecular research, based on cladistic analysis of DNA sequences, has resurrected and redefined the Polyporales (also known as the polyporoid clade). Studies using a combination of rRNA gene sequences, single-copy protein-coding genes, and genome-based phylogenetic analyses have shown that the Polyporales are a monophyletic group. They are a member of the class Agaricomycetes, but have not been assigned to a subclass. Though the precise boundaries of the order and its constituent families are yet to be resolved, it retains the core group of polypores in the family Polyporaceae, with additional species in the Fomitopsidaceae and Meripilaceae. It also includes polypores in the Ganodermataceae, which were previously assigned to their own separate order, the Ganodermatales, based on their distinctive basidiospore morphology. Corticioid fungi belonging to the Cystostereaceae, Meruliaceae, Phanerochaetaceae, and Xenasmataceae are also included, as are the cauliflower fungi in the Sparassidaceae. In an extensive molecular analysis, Manfred Binder and colleagues analyzed 6 genes from 373 species and confirmed the existence of four previously recognized lineages of Polyporales: the antrodia, core polyporoid, phlebioid, and residual polyporoid clades. Extending this work, Alfredo Justo and colleagues proposed a phylogenetic overview of the Polyporales that included a new family-level classification. They assigned family names to 18 clades and four informal unranked clades. The families are listed below, followed by their taxonomic authorities and year of publication: Other families that putatively belong to the Polyporales, but for which molecular confirmation is absent or lacking, include Diachanthodaceae Jülich, (1981); Fragiliporiaceae Y.C.Dai, B.K.Cui & C.L.Zhao (2015); Hymenogrammaceae Jülich (1981); and Phaeotrametaceae Popoff ex Piątek (2005). The Nigrofomitaceae, formerly placed in the Polyporales, was shown to be nested as a distinct lineage within the Hymenochaetales. The family Steccherinaceae was redefined in 2012 to contain most species of the poroid and hydnoid genera Antrodiella, Junghuhnia, and Steccherinum, as well as members of 12 other hydnoid and poroid genera that had been traditionally classified in the families Phanerochaetaceae, Polyporaceae, and Meruliaceae. Several new genera were added to the Steccherinaceae in 2016–17.